Intermediate Physiology Chapter 7

Match the correct neuron type with its description.

- Association Neuron: multipolar cells located entirely within the CNS - Sensory Neuron: transmits impulses from a receptor to the CNS - Motor Neuron: transmits impulses from the CNS to an effector cell

Which of the following cell types are neuroglial cells located within the peripheral nervous system?

- Schwann cells - Satellite cells

What is a cell that can change its membrane potential in response to stimulation classified as?

- an excitable cell - an irritable cell

Which of the following cell types are neuroglial cells located within the central nervous system?

- astrocytes - microglia - oligodendrocytes

Which of the following are functional classifications of neurons?

- autonomic motor neurons - sensory neurons - efferent neurons

What is the resting membrane potential of a typical neuron?

-70mV

Place the events of an excitatory synaptic transmission in the correct order chronologically.

1. action potential reaches the terminal bouton 2. voltage gated Ca2+ channels open 3. Ca2+ enters causing the release of an excitatory neurotransitter 4. neurotransmitter binds to ligand-gated channel on the postsynaptic membrane causing it to open 5. Na+ enters the postsynaptic cell causing a depolarization

Arrange the events regarding K+ and the generation of the action potential in the correct order chronologically.

1. threshold is reached 2. K+ voltage gated channels open 3. repolarization starts 4. K+ inactivation begins 5. hyperpolarization

The depolarization phase of the action potential is primarily produced by the movement of ______ ions into the axon.

Na+

The nodes of ______________ are gaps in the myelin sheath surrounding axons.

Ranvier

The cells responsible for forming the myelin sheaths around axons in the peripheral nervous system are called __________________.

Schwann cells

In the peripheral nervous system, the _____________________ form myelin sheaths around peripheral axons.

Scwann cells

What is a neurotransmitter?

a chemical released by presynaptic nerve endings that cause changes in the membrane potential or a postsynaptic cell

What is a collection of axons wrapped together in the peripheral nervous system called?

a nerve

A propagated change in the membrane potential of a neuron due to the opening and closing of voltage gated channels is called a(n) _______________________________.

action potential

According to the structural classification system, what is a neuron that has two processes, one at either end of the cell body called?

bipolar neuron

The highly selective barrier to diffusion that the specialized capillaries of the brain create is known as the _____________________ barrier.

blood brain

The ability of a neuron to conduct or transfer charges through its cytoplasm is called its ____________ property.

cable

What are the thin branching processes that provide receptive sites for incoming signals and transmit graded electrochemical impulses to the cell body?

dendrites

A sodium voltage gated channel will open in response to the __________________ of the membrane to threshold.

depolarization

The combined electrical and concentration gradient that drives that movement of ions into and out of cells is known as the:

electrochemical gradient

Myelinated axons conduct impulses _______________ than unmyelinated axons.

faster

When a dendrite is hyperpolarized, what is its effect on the possible production of a nerve impulse?

inhibitory

A drug that is classified as an antagonist:

inhibits the activity of receptor proteins

The fastest conduction velocities are seen in axons that have:

large diameter and myelination

Neurons that have several dendrites and one axon extending from the cell body are classified as:

multipolar

Some axons in both the PNS and CNS are surrounded by a(n) ______________ which increases the speed at which the axons can conduct impulses.

myelin sheath

A(n) ________________ is a cable like collection of axons in the peripheral nervous system.

nerve

In myelinated axons, action potentials occur only at the _________________________________

nodes of Ranvier

Neuronal recruitment:

occurs when more axons within a nerve become active with increase stimulus strength

The ______________________ are responsible for producing the myelin sheath that surrounds the axons in the central nervous system.

oligodendrocytes

The conduction of a signal in an axon through cable properties alone is _____________ due to the high internal resistance and the loss of ions through the membrane.

poor

A signal is conducted from the ____________ cell through the synapse to the _______________ cell.

presynaptic, postsynaptic

When a cell returns to its resting potential, the cell is undergoing ________________________.

repolarization

The __________________ classification of neurons is based on the number of processes that extend from the cell body of the neuron.

structural

A(n) _____________ is the connection between a neuron and either another neuron or an effector cell.

synapse

During the absolute refractory period of a neuron:

the axon can not respond to another stimulus no matter the strength

All axons in the peripheral nervous system are surrounded by:

the neurilemma or sheath of Schwann

Change in the permeability of the membrane are due to:

the opening and closing of ion channels

What is the potential difference in voltage across the membrane of a resting cell called?

the resting membrane potential

The minimum voltage change required for the activation of the Na+ voltage gated channels and the generation of the action potential is known as the ______________ voltage.

threshold

What is the function of the myelinated sheath around axons?

to increase conduction velocity of an axon

True or false: The action potential in each successive region of the axon serves as the generator potential or stimulus for the next segment to generate an action potential.

true

Areas of the central nervous system that contain a high concentration of axons form the ___________ matter.

white

How are capillaries in the brain different from capillaries in most other organs?

- brain capillaries do not have pores between adjacent endothelial cells - the endothelial cells in brain capillaries are joined together with tight junctions

The resting potential of a cell is produced by:

- diffusion of sodium ions into the cell - the interior of the cell membrane has an excess of negatively charged proteins - diffusion of potassium ions out of the cell - membrane permeability for potassium ions greater than sodium ions

By what mechanisms does the brain obtain molecules and nutrients from the blood?

- diffusion through endothelial capillary cells - active transport - endocytosis and exocytosis

The neuroglia or glial cells of the nervous system:

- divide by mitosis - support the functions of neurons

Match the term to its correct meaning.

- ganglion: group of neuron cell bodies in the peripheral nervous system - nucleus: group of neuron cell bodies within the central nervous system - tract: group of axons interconnecting regions of the CNS - nerve: group of axons in the peripheral nervous system

The conduction of an action potential is an unmyelinated axon:

- is conducted without decrement - is slower than in a myelinated neuron

Conduction of action potentials in a myelinated axon is:

- is faster than in an unmyelinated axon - continues without decrement - called saltatory conduction

The myelin sheath that covers some axons:

- is formed by oligodendrocytes in the CNS - increases the speed of impulse conduction - is formed by Schwann cells in the PNS

The function of myelin is to:

- prevent leakage of Na+ and K+ - provide insulation for the axon

Which of the following structures are part of the CNS?

- spinal cord - brain

Which of the following structures are part of the peripheral nervous system?

- spinal nerves - cranial nerves

What are neurons?

- the basic functional units of the nervous system - the conducting cells of the nervous system

An ion channel that opens in response to a change in the membrane potential of the cell is called a(n) _____________ channel.

- voltage-regulated - voltage-gated

The explosive increase in sodium permeability during the generation of the action potential results in a rapid change in the membrane potential of that region of the cell from ____ mV to ____ mV.

-70, +30

Put the parts or regions of the neuron in order from the direction of where a stimulus is first received to where a response stimulus is condcuted.

1. dendrites 2. cell body or soma 3. axon hillock 4. axon 5. synaptic terminal

Put the following events in chronological order.

1. initial segment of axon reaches threshold 2. voltage required sodium channels open 3. Na+ enters the cell causing depolarization 4. membrane potential becomes +30mV 5. Na+ channels become inactivated 6. membrane permeability to sodium declines

Place the events of the action potential in order chronologically.

1. threshold is reached 2. Na+ channels open fully and Na+ enters the cell 3. Na+ channels inactivated 4. K+ channels open fully and K+ leaves the cell 5. K+ channels inactivated

While not directly involved in the production of the action potential, ______________ allow it to occur by maintaining the appropriate ion gradients and helping to return the cell to its resting potential.

Na+/K+ pumps

A drug that is classified as an agonist:

activates or increases the activity of receptor proteins

An action potential is either generated to its maximum amplitude or not produced at all. That is referred to as its __________________________ property.

all or none

Which of the following axons would conduct the action potential the fastest?

an axon with the normal number of nodes in its myelin sheath

The ___________________ of the central nervous system regulate the external environment around the neurons.

astrocytes

What neuroglia cell type is thought to regulate neurogenesis in the adult brain, induce the formation of the blood-brain barrier, and release neurotransmitter chemicals that can stimulate or inhibit neurons?

astrocytes

The _____________ is a long process of the cytoplasm that conducts impulses called action potentials away from the cell body.

axon

What are the secondary branches of an axon called?

axon collaterals

The expanded area of the axon located next to the cell body is called the ____________________________.

axon hillock

The _______ matter of the CNS is composed of high concentrations of cell bodies and dendrites.

grey

The ______________ is the enlarged portion of the neuron that contains the nucleus.

cell body

What is the part of the neuron that contains the nucleus and is responsible for the production of most of the cell's macromolecules?

cell body

The brain and the spinal cord are a part of the ______________ nervous system.

central

What are the two divisions of the nervous system?

central and peripheral

In terms of their effects on the production of nerve impulses, the ______________ of a dendrite or cell body is excitatory.

depolarization

When a stimulation causes positive charges to flow into the cell and the membrane potential of the cell becomes more positive, the cell has ____________________.

depolarized

In terms of their effects on the production of nerve impulses, the _________________ of a dendrite or cell body is excitatory.

depolatization

What type of neurological cell line the ventricles of the brain and enable the production of cerebrospinal fluid?

ependymal cells

______ junctions are water filled channels of connexin proteins through which ions can pass from one cell to another.

gap

If a stimulation causes the inside of a cell to become more negative than its resting potential, the cell has undergone ________________________.

hyperpolarization

Cell "X" has a resting potential of -70mV. When its membrane potential is next measured, it has a membrane potential of -80mV. Which of the following is accurate about the cell?

it has hyperpolarized (undergone hyperpolarization)

The ____________ migrate through the central nervous system and phagocytose foreign and degenerated material.

microglia

Acetylcholine (ACh) is a _____________ that can be either excitatory or inhibitory depending upon the binding cell.

neurotransmitter

According to the structural classification of neurons, what is a neuron that has a single short process that branches to form a pair of longer processes?

pseudounipolar

The _____________________________ period of the action potential is the period of time during which only stronger than normal stimuli can initiate another action potential in the same segment of the membrane.

relative refractory

Axon potentials are conducted without decrement. What does this mean?

the action potential produced at the last region of the axon has the same strength and amplitude as that produced at the first region.

What serves as the stiumulus voltage required for the voltage gated ion channels to reach threshold in the portions of the axon after the initial segment?

the action potential produced by the initial segment then causes the next segment to reach threshold

What causes the absolute refractory period of a neuron?

the configuration and inactivation of the Na+ channels

The repolarization phase of the action potential is produced primarily by:

the efflux of K+